Solution processed and printed field effect transistors (FETs) typically require a low k dielectric layer in order to yield high charge transport mobility and ensure high charge transport mobility and ensure that the solvents used are compatible with other solution processed materials. Soluble perfluoropolymers are soluble in perfluorinated solvents that are generally orthogonal to semiconductor processes, meaning that they do not dissolve or otherwise damage the semiconductor processes. They allow top-gate devices to be made without concern for dissolving the underlying semiconductor layer. In addition, the low-k interface with the semiconductor that these perfluoropolymers provide also prevents charge trapping at the interface for both electrons and holes, typically leading to high charge transport mobilities for solution processed organic semiconductors.
These two factors allow a single dielectric material to be used for both FET polarities in complementary circuits, greatly simplifying the production of these circuits. However, using these materials has some downsides. The low dielectric constant (k) of these materials leads to low capacitance and therefore high operating voltages. To reduce the operating voltages, the processes try to keep the dielectric as thin as possible. In printed FETs, the underlying layers may be rough. The process may have difficulties producing pin-hole free films. Thinning the dielectric to give the desired operating voltage can lead to significant amounts of gate leakage. In addition, perfluoropolymer dielectric has a very low surface energy that makes further solution processing on top of it difficult without further surface modification.